Deepwater drillers Transocean, Diamond and Noble will be key beneficiaries as oil supplies get tighter and prices trend higher.

Shares of deepwater drillers caught fire this month, bouncing 20% to 25% from early-March lows, putting them smack in the vanguard of the market's powerful rally. Those eye-popping gains, of course, came from severely depressed levels. And, even after the move, shares of the big offshore names are far below last year's highs. Transocean, for example, fetches $61, down from $163. Diamond Offshore...